What effect does weight loss have on resting energy expenditure?

Weight loss typically leads to a decrease in resting energy expenditure (REE). This phenomenon occurs primarily because when an individual loses weight, there is a reduction in the amount of body tissue, including fat and lean mass. The resting energy expenditure is largely determined by the total body mass and the proportion of lean body mass compared to fat mass. Lean mass is metabolically active tissue, meaning it requires more energy to maintain than fat tissue.

As body weight reduces, there is an overall decrease in total energy needs, which is reflected in the reduced resting energy expenditure. This decreased caloric requirement can present challenges in maintaining weight loss, as individuals may find that they need to adjust their caloric intake downwards to continue losing weight or to prevent weight regain.

The other options suggest conflicting effects on REE that do not align with the physiological understanding of how weight loss impacts energy expenditure.